This invention relates to an apparatus for determining the charging profile on the charging surface of a shaft furnace. More particularly, this invention relates to an apparatus (profilometer) for determining the charging profile which consists of a plurality of level probes, each probe including a weight which is suspended vertically above the charging surface on the first end of a cable which projects from a supporting arm. The second end of each of these cables, in turn, is connected outside the furnace to respective winding drums, each drum being controlled by a driving device which raises or lowers the probe connected to the drum. This invention also consists of a monitoring device for measuring the unwinding of the cable from the drum and the descent of the probe onto the charging surface as well as a method of replacing an individual probe and its cable from outside the shaft furnace.
The profile of the charging surface of a shaft furnace, particularly a blast furnace, is currently determined or measured using essentially two factors. One of these factors is the distribution of charging material as it is introduced into the furnace and the second factor is the descent of the material within the furnace. It should be understood that the term "profile" indicates the particular surface configuration which the material being charged to a shaft furnace forms on the burden of the furnace.
Although it is extremely difficult, if not impossible, to control the descent of charging material in a shaft furnace, the relatively recent development of bell-less top type furnaces has made it possible not only to produce any desired distribution profile of charged material, but also, where appropriate, to correct or rectify the profile on the charging surface. As a result, a charging device in a bell-less top type shaft furnace offers the possibility of controlling the change in the profile of the charging surface during the operation of the blast furnace, provided that this profile can be determined. Accordingly, in order to control the profile of the charging surface of a shaft furnace of the bell-less top type, it is extremely important to provide an apparatus for determining the actual profile of the charging surface at any given point in time.
Unforunately, prior art profile determining apparatii have all suffered from various deficiencies and drawbacks. Typically, such charging surface profiles have been determined by an approximate estimate thereof, based on level measurements carried out along several different points in the shaft furnace by means of vertical mechanical probes mounted at one end of the furnace.
In an effort to improve such profile determinations, attempts have recently been made to develop radiation profilometers to obtain an acurate and complete reproduction of the profile over the entire charging surface. However, these radiation profilometers have not yet been developed to the stage were they can be efficiently used on an industrial scale due to serious problems caused by the severe conditions prevailing in the furnace and also due to the extremely high cost of such radiation devices.
As a result, those skilled in the art have attempted to improve prior art vertical level probes (discussed above) so as to obtain a better approximation of the charging profile German patent application Ser. No. A1-3,123,944 is an example of an improved device having multiple probes for simultaneously taking measurements at several points located on a radial line at the surface of the burden of a shaft furnace.
However, the device disclosed in the German patent application has been designed so as to operate with a single common drive mechanism for all of the individual probes and as a result, has been unusually difficult to manufacture. In fact, the numerous guide and return pulleys for the cables complicate maintenance and risk causing premature wear thereof. Moreover, raising the individual probes from the charging surface results in raising the loose pulleys before the probes are disengaged from the surface. This not only lengthens the duration of the measuring operation, but also forces the probes to rest on the material longer than is necessary (which may result in excellerated wear of the probes due to the extremely harsh conditions). Also, the many pulleys necessary for each individual probe makes the device of the German Patent Application very bulky and therefore undesirable.